Etude thermocinetique des phenomenes de dissolution par calorimetrie Calvet a haute temperature dissolution d'alumines dans la cryolithe

Although the thermal curves given by a Calvet calorimeter can be considered representative of the thermogenesis of slow phenomena, this is not the case for the brief thermal effects of dissolution, for example, which need typically no more than twenty minutes. At high temperatures, a numerical method of deconvolution of the recorded signal was applied in order to obtain the proper thermogenesis of the phenomenon. The time constants of the calorimeter were determined from thermal effects due to the dropping into the bath of small quantities of silver and platinum. The method was applied to the dissolution of a-alumina and industrial aluminas in cryolithic baths at 1290 K. The different kinds of alumina could be classified according to their time of dissolution. The dependence of the alumina concentration of the bath on the dissolution rate was also investigated.

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Zusammenfassung Die mittels eines Calvet-Kalorimeters erhaltenen thermischen Kurven sind zwar repräsentativ für langsame Phänomene der Thermogenese, nicht jedoch für kurzzeitige thermische Effekte wie z. B. ein Inlösunggehen, das im allgemeinen nicht mehr als 20 Minuten dauert. In solchen Fällen wurde für hohe Temperaturen eine numerische Methode zur Zerlegung des registrierten Signals angewandt, um die reine Thermogenese der Phänomens zu erhalten. Zeitkonstanten des Kalorimeters wurden aus den thermischen Effekten bestimmt, die beim Einwerfen kleiner Silber- und Platinmengen in das Bad auftraten. Die Methode wurde zur Untersuchung der Auflösung von -Aluminiumoxid und industriellen Aluminiumoxidproben in Kryolithbädern bei 1290 K herangezogen. Die verschiedenen Aluminiumoxidarten konnten nach der zur Auflösung notwendigen Zeit klassifiziert werden. Die Abhängigkeit der Auflösungsgeschwindigkeit von der Aluminiumoxidkonzentration des Bades wurde ebenfalls untersucht.

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, , . , , , , . , . , . - 1290 K. . .

     

Effect of the Nucleophile Structure on the Relative Mobility of the Nitro Group and Fluorine Atom in Reactions of 3,5-Dinitro- and 3-Fluoro-5-nitrobenzotrifluorides with Phenols in the Presence of Potassium Carbonate

The relative mobility of the nitro group and fluorine atom in 3,5-dinitro- and 3-fluoro-5-nitrobenzofluorides was estimated by the competing reaction technique using phenols in the presence of potassium carbonate (DMF, 65-95°C). Correlation analysis of the relative rate constants k(NO₂)/k(F) and of the differences in the activation parameters (H and S ) of competing reactions showed the existence of two reaction series for the examined phenols. The higher mobility of the nitro group was found to result from the entropy control of the reactivity of arenes. The mechanism of these reactions is discussed.     

Kinetics and mechanism of monomolecular heterolysis of commercial organohalogen compounds: XXXVIII. Correlation analysis of solvent effects on the activation parameters of heterolysis of <Emphasis Type="Italic">t</Emphasis>-BuBr and <Emphasis Type="Italic">t</Emphasis>-BuI

Heterolysis of t-BuBr and t-BuI in aprotic solvents involves a H - S compensation effect. The G of t-BuBr heterolysis in aprotic solvents decreases with increasing solvent polarity and cohesion, whereas the respective value for t-BuI heterolysis decreases with increasing solvent polarity, nucleophilicity, and polarizability. In protic solvents, a negative effect of nucleophilic solvation is observed.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 9, 2004, pp. 1476–1483.Original Russian Text Copyright © 2004 by Ponomarev, Zaliznyi, Dvorko.This revised version was published online in April 2005 with a corrected cover date.     

Transformed steroids. 176. Paths of transformation of 17a-ethynyl-17β-hydroxyandrostenes into Δ16-21-hydroxy-20-ketopregnenes

A novel method in steroid chemistry for synthesis of pregna-4,16-dien-3-one-20-yne and pregna-5,16-dien-3-ol-20-yne, based on the dehydration of Co-complexes of the corresponding 17-ethynyl-17-carbinols was investigated. The theoretical possibility of using phenyliodoso trifluoroacetate for the preparative transformation ¹⁶-17-ethynyl steroids into 21-hydroxy-¹⁶-20-ketopregnanes was discovered.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2810–2815, December, 1989.     

Pyrroles from ketoximes and acetylene. 14. Quantitative estimate of the effect of substituents on the NH acidities of pyrroles

The pK values of a series of substituted pyrroles and the vNH values (in dimethylformamide), which characterize their relative acidities were measured by the transmetallation method. It was established that the acidities of pyrroles are determined primarily by the inductive effect of the substituents and are virtually independent of the ability of the latter to enter into conjugation with the ring. This means that the electron pair of the anion that is set free in the ionization of pyrrole retains character. The linear dependences of the pK and NH values on the inductive constants (I) of the substituents can be used to estimate the pK values of various compounds that contain a pyrrole ring starting from the NH and I values.See [1] for communication 13.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 632–638, May, 1980.     

About the adequacy of reference materials

Summary Any analytical procedure includes at least six steps: (1) the sampling; (2) the conditioning of the sample after sampling and its transport to the analytical laboratory; (3) the treatment of the sample at the laboratory; (4) the introduction of the sample into the measurement system; (5) the measurement itself; (6) the processing of the analytical signal and its results. We propose to measure the adequacy of an RM by the factor =^x/^RM, where ^x and ^RM are the errors associated with the analysis of a sample (x) and the RM, respectively. A factor _i can be defined for each step i of the analytical process. The paper examines the means of estimating the parameters _i ^x , _i ^RM and _i for each step of the analytical process. All _i ^x terms excluding those related to the sample treatment and to the measurement can be measured without the use of an RM. To determine the error to be expected from the sample preparation and the measurement it is sufficient to use am RM which is taylored to these two steps only, rather than to the entire analytical process. This may be done for example by spiking a sample with an RM providing the necessary analytical signal. Such RMs are simple and inexpensive to prepare and have very broad applications.     

Ring-Ring Tautomerism in the Series of Isoxazolidine and Δ2-Isoxazoline Derivatives

We have studied the reaction of 5-hydroxy-3,3,5-trimethylisoxazolidine and 5-hydroxy-3,5-dimethyl-²-isoxazoline with derivatives of thiosemicarbazide and also thiocarbonohydrazine. Both reactions serve as a method for synthesis of the previously unknown 5-thiosemicarbazido(thiocarbonohydrazino)isoxazolidines and -²-isoxazolines. ¹H and ¹³C NMR spectroscopy revealed a tendency of the indicated compounds toward ring-chain and ring-ring tautomeric conversions in solutions involving the 1,2,4-triazolidine, ²-pyrazoline, and 1,2,4,5-tetrazine rings.     

Synthesis of furan analogs of 1, 3, 5-triphenylpyrazoline derivatives

Furan analogs of chalcones are condensed with phenylhydrazine to give a number of ²-pyrazolines hitherto not described in the literature. It is shown that in , -unsaturated ketones, a nitro-group in the nucleus and remote from the carbonyl group makes cyclization to the corresponding ²-pyrazolines more difficult than does one adjacent to the carbonyl.     

Solvent effects on substitution reactions at complexes of the [Fe(CN)5L]3- type in binary aqueous mixtures

Summary The kinetics of replacement of 4,4-bipyridine, (4,4-bipy), and 4-cyanopyridine, (4-CNpy), by cyanide in [Fe(CN)₅-(4,4-bipy)]^3-. at 298 K have been studied in binary aqueous mixtures containing different amounts of t-butanol, methanol, glycerol, ethyleneglycol and sucrose. The plots of logarithms of the limiting rate constantsversus the mole fraction of water are linear over the entire composition range studied, showing the importance of solvation phenomena. A different straight line of log (k_L/s^–1)versus X_H2O is obtained for each mixture, indicating the influence of other solvent parameters on the reaction rate. A multiparameter regression of G _exp with A (acidity vector), B (basicity vector) and G^E is used for both reactions; plots of G _calc versus G _exp are linear with slopes of near unity.     

Synthesis and rotatory dispersion of cisoid bicyclic enamino ketones

Optically active cisoid, bicyclic, enamino ketones — N-(-phenylethyl)-4-keto-^9,10-octa-hydroquinoline and N-(-phenylethyl)-4-keto-^8,9-hexahydropyridine — were synthesized by the condensation of ethyl -[N-(-phenylethyl)amino]propionate with cyclohexanone and cyclopentanone, while ethyl -(N-benzylamino)propionate and cyclohexanone gave N-benzyl-4-keto-^9,10-octahydroquinoline. A study of the rotatory dispersion of the compounds obtained demonstrated that a strong positive Cotton effect at 330–350 nm, which is associated with the presence of a cis-enamino ketone chromophore, is characteristic for them.Communication XXVIII of the series Stereochemical Investigations. See [1] for communication XXVII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 541–545, April, 1972.     

Kinetics and mechanism of Os(VIII) catalyzed oxidation of dimethyl sulfoxide by vanadium(V)

The title reaction is first order each in vanadium(V) and Os(VIII) and fractional order with respect to DMSO. The rate is found to decrease with increasing concentrations of sulfuric, perchloric and acetic acid, whereas the rate increases with the increasing concentrations of sodium bisulfate and sodium perchlorate. Thermodynamic parameters like E_a, H, S and G were evaluated. A suitable mechanism consistent with the observed kinetics is proposed.     

Synthesis of 3β-fluoro derivatives of 7-dehydrocholesterol and of ergosterol

It has been established that the fluorination of 3-hydroxy-^5,7-steroids, unlike that of 3-hydroxy-⁵-steroids, does not lead to the formation of 3-fluoro derivatives. The reaction products are 3,5-cyclo-^6,8(14) compounds. Consequently, to obtain the 3-fluoro derivatives of provitamins D — 7-dehydrocholesterol and ergosterol — the 5,7-diene system was first protected by the formation of a cyclo-adduct with 4-phenyl-1,2,4-triazoline-3,5-dione after which the adduct was fluorinated with morpholinosulfur trifluoride to the 3-fluoro adduct, and then the 5,7-double bonds were regenerated by treating the adduct with a solution of sodium methanolate in methanol.A. V. Palladin Institute of Biochemistry, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 102–107, January–February, 1985.     

Analysis of steroids. XVI

Summary ⁴-3-Hydroxy- or -acetoxysteroids can be determined as 3,5-dienes by spectrophotometry at 236 nm. This method has been employed for the determination of ethynodiol in contraceptive pills. Possible interferences by co-extracted foreign substances have been prevented by differential spectrophotometry. A combination of this method with the reduction by means of sodium borohydride made possible a determination of ⁴-3-ketosteroid contamination in norethynodrel.

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Analyse von Steroiden. XVI

Zusammenfassung ⁴-3-Hydroxy- oder Acetoxysteroide können in Form von 3,5-Dienen spektrophotometrisch bei 236 nm bestimmt werden. Das Verfahren wurde zur Bestimmung von Ethynodiol in Anticoncipientia verwendet, wobei Störungen durch mitextrahierte Fremdsubstanzen durch Differentialspektrophotometrie verhindert wurden. Durch Kombination dieser Methode mit der Reduktion durch Natriumborhydrid konnte eine Verunreinigung von ⁴-3-Ketosteroid in Norethynodrel bestimmt werden.

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Part of the lecture Differential Spectrophotometry in Pharmaceutical Analysis presented to the F.I.P. Congress, London, September, 1969. Part XV.: Mikrochim. Acta (in press).

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The authors thank Mrs. G. Berhidai, Miss M. Kapàs and Miss J. Sütö for their technical assistance.     

The electronic spectrum of VCr

The electronic spectrum of VCr has been studied using the complete-active-space self-consistent field complete-active-space second-order perturbation theory approach. Potential-energy curves for 12 electronic states have been computed. Transition energies, with respect to the X² ground state, for some of the calculated electronic states are (with possible experimental values within parentheses) 0.53 eV (0.56) for A²⁺, 1.03 eV (1.14) for A⁴, 1.20 eV (1.14) for B², 1.45 eV (1.51) for B⁴, 1.60 eV (1.51, 1.78) for C², and 1.61 eV (1.63) for A^4–. AcknowledgementsThe research reported in this communication was supported by a grant from the Swedish Natural Science Research Council (NFR). S. Alex and D.G. Leopold are acknowledged for providing results from their negative ion photoelectron spectroscopy on VCr.Contribution to Björn Roos Honorary Issue     

Sterine in Weidegräsern

During the course of investigations concerned with a cattle disease (Weidekrankheit) in Austrian alpine regions, it became of interest to examine the sterol fractions of some typical grasing plants, since it seemed possible that a biological connection exists between the phytosterols, Vitamin D and related compounds and the cause of the Weidekrankheit.The sterol contents of eight different species of Austrian alpine grasses especially of Trisetum flavescens, were studied by gas-liquid chromatography and mass spectrometry. All contained sitosterol as the main component, besides cholesterol, campesterol, stigmasterol, ⁷-cholestenol and ^{7,24 (28)}-stigmastadienol.The aim of this examination was to establish whether there is an influence of fertilizing on the content of the above mentioned compounds: no remarkable difference between the sterol contents of fertilized and non-fertilized grasses could be found.     

Marginal electron density and density-difference functions

Summary For visual analysis of the density reorganization and distortion, the one-dimensional cut (x, y ₀,z ₀) and the two-dimensional cut (x, y, z ₀) of the three-dimensional electron density difference function (x, y, z) are frequently employed. However, these cut functions do not satisfy any sum rules in contrast to the original difference function (x, y, z). To avoid this difficulty, the use of the marginal electron density functions _x (x) and _xy (x, y) and their difference functions _x (x) and _xy (x, y) is proposed. The marginal densities are condensation of the three-dimensional density onto a particular plane or line of our interest, and they satisfy the sum rule (i.e., the conservation of the number of electrons) exactly. Some basic properties of the marginal electron density are clarified for typical diatomic molecular orbitals. An illustrative application is given for the bonding and antibonding processes in the H₂ system.     

Optical and electrical measurements on CO2 covered copper films

Thin polycrystalline copper films are deposited in a special UHV cell on glass substrates and are covered step by step with CO₂. The optical and electrical properties of the films are studied in-situ by means of ellipsometry and resistivity measurements. The properties of the clean films correspond to literature data. In the case of monolayer adsorption of CO₂, the changes in the ellipsometrical angles are +1° and +0.1°, similar to the Cu/O and Cu/CO systems. Three-dimensional island growth leads to a drastical increase of and by several orders of magnitude. The resistivity first quickly decreases and then slowly reapproaches the initial value. This marked kinetics is quantitatively interpreted on the basis of a diffusion model.     

Halogen-containing Pyridines. 8. Synthesis of 3,5-Dichloropyridines Containing Pyrazole and Pyrazoline Residues in Position 2

The interaction of 3,5-dichloro-2-pyridylhydrazine with ,-unsaturated carbonyl compounds leads to 1-(3,5-dichloro-2-pyridyl)-3,5-disubstituted ²-pyrazolines. It was shown that N-(3,5-dichloro-2-pyridyl)hydrazones of the corresponding aldehydes and ketones are formed as intermediates. Condensation of the hydrazine mentioned above with ,-diketones gives 1,3,5-trisubstituted pyrazoles, but with acetoacetic ester a 1,3-disubstituted pyrazol-5-one containing a 3,5-dichloropyridyl residue is obtained.     

Absorption spectra of 2-styryl-4-phenyl-thiazole ethiodides in organic solvents of varying polarities and determination of the formation constant of the charge transfer complex formed

The electronic absorption spectra of some 2-styryl-4-phenyl-thiazole ethiodides are studied in organic solvents of different polarities. The shorter wavelength band appearing in the visible region is assigned to an intramolecular charge transfer (CT)-transition originating from the phenyl moiety to the positively charged hetero ring, while the longer wavelength one is due to an intermolecular CT-transition from the iodide ion to the 2-styryl-4-phenyl-thiazolinium cation. These assignments are based on the nature of the aldehydic residue and effects of solvent, concentration, and temperature on both the position and absorptivity of the CT complex-band. It is concluded that the CT complex formed will be highly solvated inDMF, DMSO, ethanol and methanol relative to in CHCl₃, dioxane and acetone. The formation constant of the CT complex in solutions of different polarities is determined at different temperatures. Furthermore, the thermodynamic parameters H ^o, G ^o and S ^o for complex formation are calculated and discussed.

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Absorptionsspektren von 2-Styryl-4-phenyl-thiazol-ethiodiden in verschiedenen Lösungsmitteln und Bestimmung der Bildungskonstanten der Charge-Transfer-Komplexe

Zusammenfassung Die Elektronenanregungsspektren einiger substituierter 2-Styryl-4-phenyl-thiazol-ethiodide wurden in einigen Lösungsmitteln unterschiedlicher Polarität untersucht. Die Absorption bei kürzerer Wellenlänge wird einem intramolekularen Charge-Transfer (CT)-Übergang zugeordnet, die langwellige Bande einem intermolekularen CT-Übergang (Jodid—organ. Kation). Die Diskussion erfolgt basierend auf Substitutions-, Lösungsmittel-, Konzentrations-, und Temperatur-Effekten. Die Komplexbildungskonstanten und die thermodynamischen Parameter H ^o, G ^o und S ^o werden angegeben.

     

On the relationship between the structures of Cu(II) complexes and their chemical transformations IX

The Stoichiometry and the kinetics of thermal decomposition of the title compounds were studied. The results were correlated with the structures of the Cu(II) coordination polyhedra, which have in general a 4+2 type of coordination. It was shown that the equatorial Cu-H₂O bond distances are important for the found decomposition stoichiometries. As an intermediate of thermal decomposition, Cu(H₂O)₅(CH₃C₆H₄SO₃)₂ was prepared and characterized via its IR and electronic spectra and powder X-ray diffractogram. The experimental activation energies increase with increasing degree of tetragonality of the Cu(II) coordination polyhedron forX ^–=C₆H₅SO₃ and D-C₁₀ H ₁₅OSO₃, but decrease forX ^–=4-CH₃C₆H₄SO₃. TheE ^* value found for the decomposition of the latter compound can not be attributed to the chemical reaction.

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Zusammenfassung Die Stöchiometrie und Kinetik der thermischen Zersetzung der Titelverbidungen wurde untersucht. Die Ergebnissen wurden auf die Strukturen der Cu(II) Koordinationspolyeder bezogen, die im allgemeinen eine 4+2 Koordination aufweisen. Die Länge der äquatorialen Cu-H₂O Bindung erwies sich als bedeutungsvoll für die ermittelte Stöchiometrie der Zersetzung. Das Zwischenprodukt Cu(H₂O)₅(CH₃C₆H₄SO₃)₂ der thermischen Zersetzung wurde dargestellt und mittels IR- und Elektronenspektren sowie Röntgenpulveraufnahmen beschrieben. Mit ansteigendem Tetragonalitätscharakter der Cu(II) Koordinationspolyeder wachsen die experimentell ermittelten Aktivierungsenergien fürX ^–=C₆H₅SO₃ und D-C₁₀H₁₅OSO₃ an, nehmen aber fürX ^–= 4-CH₃C₆H₄SO₃ ab. Der für letztere Verbindung ermittelteE ^* Wert kann der chemischen Reaktion nicht zugeschrieben werden.

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. , 4 + 2. , Cu-H₂O . Cu(H₂O)₅(CH₃C₆H₄SO₃)₂ , -. X ^–=C₆H₅SO₃ -C₁₀H₁₅OSO₃, X ^–= 4-CH₃C₆H₄SO₃. .